Presently, various types of thermometers exist for industrial applications. The most commonly used industrial thermometer is the platinum resistance thermometer (PRT) for temperatures ranging from −196° C. to 500° C. when measurement uncertainties of less than or equal to 10 mK (millikelvin) are required. The platinum resistance thermometer exploits a predictable change in electrical resistance of platinum with changing temperature. Platinum resistance thermometers offer high accuracy, low drift, a wide operating range, and suitability for applications that require precise measurements.
However, platinum resistance thermometers are extremely sensitive to mechanical shock in handling and shipping. Shocks change the physical state of the annealed, loosely supported platinum resistance element. These changes often prevent a platinum resistance thermometer from meeting the measurement uncertainty [10_mK (0.01° C.)] required in industrial applications. Indeed, as described in the publication of Strouse, entitled “Sapphire whispering Gallery Thermometer,” Int J Thermophysics (2007) 28:1812-1821, recent studies have shown that a shift of 1 mK in the magnitude of a platinum resistance thermometer is 20 times greater than the calibration uncertainty and can cause an error in the temperature of the measurement by as much as 30 mK at high temperatures.
Furthermore, an AC resistance bridge is typically required as a readout device for standard platinum resistance thermometers. However, AC resistant bridges typically cost between $50,000 and $75,000.
Accordingly, there is a need for an improved, cost effective industrial thermometer having improved stability, resistance to mechanical shock, and greater certainty in temperature measurements.